A reference voltage generator can use a power supply voltage as a reference point for generating a reference voltage by a resistor divider technique when the percentage variation in power supply voltage is no greater than that required for the reference voltage. Advantages of this technique are that the circuit is simple and can be made to require very little power. A circuit, of the closest known prior art, uses this technique and is shown in FIG. 1. When the variation in power supply voltage is too great, then techniques for compensating for power supply voltage variation must be used. Conventional techniques include zener diode references and bandgap references. Both are power consuming bipolar techniques which, although potentially very accurate, may be undesirable for some uses, particularly where power consumption is a major consideration. In addition, zener diodes can be difficult to manufacture with adequate control in an MOS process.